Manufacturing of Valves (Part Two)

4. The Process Planning of Valve Parts
A valve only has a few of major parts. The simple structure, the inaccurate machining and the rough external surface of the major parts leave people an impression that the major parts are just the simple components. Actually, the precision of the core sealing parts of valves should be extremely accurate, and the requirements on the flatness, smooth finish, hardness of the sealing surface, goodness of fit of sealed auxiliaries are also greatly high. All these become the most difficult parts in the machining process of valves.

5. Testing and Inspection for Valves
The valve is the important start-stop and regulatory element of pressure pipelines, while pressure pipelines have different working conditions such as high temperature and high pressure working conditions, low temperature and deep cooling working conditions and flammable as well as explosive medium conditions. However, the inspection and testing conditions of valve manufactures can not meet the requirements of the actual working conditions of valves. Various valve testing standards at home and aboard stipulate that the test should be conducted by using gas or water as the medium under the room temperature. Therefore, the fundamental existing potential hazard is that the valve products passing the factory tests may be unable to meet the operating requirements in the practical use under harsh working conditions due to the improper material selection, poor casting quality and damages on sealing performance. Momentous quality accidents will even be triggered.

The Manufacturing Process of Valves
The First Step: The Manufacturing Process of the Valve Body
The manufacturing process of the valve body consists of the following steps: procurement of castings (according to the standard), the factory inspection (according to the standard), ultrasonic flaw detection of the overlaying groove (according to the pattern), overlaying, the heat treatment after overlaying, finish machining, grinding the sealing surface, the hardness inspection of the sealing surface and the dye penetrant inspection.

The Second Step: The Manufacturing Process of Valve Internals Parts
A. The internal parts such as the valve clack and the valve seat, needing the overlaying of the sealing surface
The manufacturing process of the valve's internal parts consists of the following steps: procurement of castings(according to the standard), the factory inspection(according to the standard), manufacturer of blanks(the round steel or the forge piece, according to the technological requirements of the drawing), rough machining of the ultrasonic testing surface(according to the pattern), rough machining of the overlaying groove, overlaying, the heat treatment after overlaying, finish machining, grinding the sealing surface, the hardness inspection of the sealing surface and the dye penetrant inspection.

B. Valve stems
The manufacturing process of the valve stem consists of the following steps: procurement of castings(according to the standard), the factory inspection(according to the standard), manufacturer of blanks(the round steel or the forge piece, according to the technological requirements of the drawing), rough machining of the overlaying groove, overlaying, the heat treatment after overlaying, finish machining, grinding the outer edge, the surface treatment of the valve stem(nitridation, quenching, chemical plating), the terminal treatment (polishing, grinding, etc.), grinding the sealing surface, the hardness inspection of the sealing surface and the dye penetrant inspection.
Aug 21,2017
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